Supported chromium-molybdenum and tungsten sulfide catalysts

ABSTRACT

Supported hydroprocessing catalysts comprising a sulfide of trivalent chromium and molybdenum or tungsten which optionally may contain one or more promotor metals such as Co, Fe, Ni and mixture thereof. These catalysts are obtained by comprising a preselected quantity of support material with a precursor salt containing a tetrathiometallate anion of Mo or W and a cation comprising trivalent chromium and, optionally, one or more promoter metals wherein both said trivalent chromium and promoter metal are chelated by at least one neutral, nitrogen-containing polydentate ligand and heating the composite in the presence of sulfur and hydrogen in an oxygen-free atmosphere. These catalysts have high selectivity for nitrogen removal. The chromium and promoter metal do not have to be in the same cation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for the preparation of supported,chromium-containing molybdenum and/or tungsten sulfide catalysts, thesupported species prepared by such process, and to the use of suchsupported catalysts for hydroprocessing processes, particularlyhydrotreating. More particularly, this invention relates to thepreparation and use of supported catalysts useful for hydroprocessingprocesses such as hydrotreating wherein said catalysts are formed byheating, at elevated temperature, in the presence of sulfur and underoxygen-free conditions, a composite of a support material and one ormore precursor compounds selected from the group consisting of [Cr_(1-z)M_(z) LX_(y) ][MoS₄ ]_(n), [Cr_(1-z) M_(z) LX_(y) ][WS₄ ]_(n) andmixture thereof wherein the chromium is in the trivalent state, whereinn=(3-z-y)/2, wherein M is one or more divalent promoter metals selectedfrom the group consisting of Mn, Fe, Co, Ni, Cu, Zn and mixturesthereof, wherein 1>z≧0 and 1-z≧y≧0, wherein L is one or more neutralnitrogen-containing ligands, at least one of which is a chelatingpolydentate ligand, and wherein X is a singly charged anionic ligand.

2. Background of the Disclosure

The petroleum industry is increasingly turning to heavy crudes, resids,coal and tar sands as sources for future feedstocks. Feedstocks derivedfrom these heavy materials contain more sulfur and nitrogen thanfeedstocks derived from more conventional crude oils. These feedstherefore require a considerable amount of upgrading in order to obtainusable products therefrom, such upgrading or refining generally beingaccomplished by hydrotreating processes which are well-known in thepetroleum industry.

These processes require the treating with hydrogen of varioushydrocarbon fractions, or whole heavy feeds, or feestocks, in thepresence of hydrotreating catalysts to effect conversion of at least aportion of the feeds, or feestocks to lower molecular weighthydrocarbons, or to effect the removal of unwanted components, orcompounds, or their conversion to innocuous or less undesirablecompounds. Hydrotreating may be applied to a variety of feedstocks,e.g., solvents, light, middle, or heavy distillate feeds and residualfeeds, or fuels. In hydrotreating relatively light feeds, the feeds aretreated with hydrogen, often to improve odor, color, stability,combustion characteristics and the like. Unsaturated hydrocarbons arehydrogenated. Suflur and nitrogen are removed in such treatments. In thehydrodesulfurization (HDS) of heavier feedstocks, or residua, the sulfurcompounds are hydrogenated and cracked. Carbon-sulfur bonds are broken,and the sulfur for the most part is converted to hydrogen sulfide whichis removed as a gas from the process. Hydrodenitrogenation (HDN), tosome degree also generally accompanies hydrodesulfurization reactions.In the hydrodenitrogenation of heavier feedstocks, or residua, thenitrogen compounds are hydrogenated and cracked. Carbon-nitrogen bondsare broken, and the nitrogen is converted to ammonia and evolved fromthe process. Hydrodesulfurization, to some degree also generallyaccompanies hydrodenitrogenation reactions. In the hydrodesulfurizationof relatively heavy feedstocks, emphasis is on the removal of sulfurfrom the feedstock. In the hydrodenitrogenation of relatively heavyfeedstocks emphasis is on the removal of nitrogen from the feedstock.Albeit, although hydrodesulfurization and hydrodenitrogenation reactionsgenerally occur together, it is usually far more difficult to achieveeffective hydrodenitrogenation of feedstocks than hydrodesulfurizationof feedstocks.

Catalyst precursors most commonly used for these hydrotreating reactionsinclude materials such as cobalt molybdate on alumina, nickel molybdateon alumina, cobalt molybdate promoted with nickel, nickel tungstate,etc. Also, it is well-known to those skilled in the art to use certaintransition metal sulfides such as cobalt and molybdenum sulfides andmixtures thereof to upgrade oils containing sulfur and nitrogencompounds by catalytically removing such compounds in the presence ofhydrogen, which processes are collectively known as hydrotreating orhydrorefining processes, it being understood that hydrorefining alsoincludes some hydrogenation of aromatic and unsaturated aliphatichydrocarbons. Thus, U.S. Pat. No. 2,914,462 discloses the use ofmolybdenum sulfide for hydrodesulfurizing gas oil and U.S. Pat. No.3,148,135 discloses the use of molybdenum sulfide for hydrorefiningsulfur and nitrogen-containing hydrocarbon oils. U.S. Pat. No.2,715,603, discloses the use of molybdenum sulfide as a catalyst for thehydrogenation of heavy oils. Molybdenum and tungsten sulfides have otheruses as catalysts in reactions such as hydrogenation, methanation, andwater gas shift.

In general, with molybdenum and other transition metal sulfide catalystsas well as with other types of catalysts, higher catalyst surface areasresult in more active catalysts than similar catalysts with lowersurface areas. Thus, those skilled in the art are constantly trying toachieve catalysts that have higher surface areas. More recently, it hasbeen disclosed in U.S. Pat. Nos. 4,243,553 and 4,243,554 that molybdenumsulfide catalysts of relatively high surface area may be obtained bythermally decomposing selected thiomolybdate salts at temperaturesranging from 300°-800° C. in the presence of essentially oxygen-freeatmospheres. Suitable atmospheres are disclosed as consisting of argon,vacuum, nitrogen and hydrogen. In U.S. Pat. No. 4,243,554 an ammoniumthiomolybdate salt is decomposed by raising the temperature at a rate inexcess of 15° C. per minute, whereas in U.S. Pat. No. 4,243,553, asubstituted ammonium thiomolybdate salt is thermally decomposed at avery slow heating rate of from about 0.5° to 2° C./min. The processesdisclosed in these patents are claimed to produce molybdenum disulfidecatalysts having superior properties for water gas shift and methanationreactions and for catalyzed hydrogenation or hydrotreating reactions.

Catalysts comprising molybdenum sulfide in combination with other metalsulfides are also known. Thus, U.S. Pat. No. 2,891,003 discloses aniron-chromium combination for desulfurizing olefinic gasoline fractions;U.S. Pat. No. 3,116,234 discloses Cr-Mo and also Mo with Fe and/or Crand/or Ni for HDS; U.S. Pat. No. 3,265,615 discloses Cr-Mo for HDN andHDS; U.S. Pat. No. 3,245,903 discloses Fe-Mo and Fe-Co-Mo for lube oilrefining; U.S. Pat. No. 3,459,656 discloses Ni-Co-Mo for HDS; U.S. Pat.No. 4,108,761 discloses Fe-Ni-Mo for HDN and U.S. Pat. No. 4,171,258discloses Fe-Cr-Mo for HDS with steam.

SUMMARY OF THE INVENTION

This invention relates to a process for the preparation of supported,chromium-containing molybdenum and/or tungsten sulfide catalysts, thesupported species prepared by such process, and to the use of suchsupported catalysts for hydroprocessing processes, particularlyhydrotreating. More particularly, this invention relates to thepreparation and use of supported catalysts useful for hydroprocessingprocesses such as hydrotreating wherein said catalysts are formed byheating, at elevated temperature, in the presence of sulfur and underoxygen-free conditions, a composite of a support material and one ormore precursor compounds selected from the group consisting of [Cr_(1-z)M_(z) LX_(y) ][MoS₄ ]_(n), [Cr_(1-z) M_(z) LX_(y) ][W S₄ ]_(n) andmixture thereof wherein the chromium is in the trivalent state, whereinn=(3-z-y)/2, wherein M is one or more divalent promoter metals selectedfrom the group consisting of Mn, Fe, Co, Ni, Cu, Zn and mixturesthereof, wherein 1>z≧0 and 1-z≧y≧0, wherein L is one or more neutralnitrogen-containing ligands, at least one of which is a chelatingpolydentate ligand, and wherein X is a singly charged anionic ligand.

By way of illustrative, but non-limiting examples, the compositions ofthis invention can comprise a supported sulfide of two metals such as Moand trivalent chromium. In another embodiment the compositions of thisinvention can comprise supported sulfide of three metals such as Mo,trivalent chromium and a promoter metal such as Ni. Thus, the supportedsulfide of this invention may or may not contain one or more promotermetals, but it must contain trivalent chromium and Mo, W or mixturethereof. Preferably the additional metal, if present, will be selectedfrom the group consisting of Fe, Ni, Co, Mn and mixtures thereof.

In a particularly preferred embodiment ligand L will be three bidentateor two tridentate chelating amines and the oxygen-free conditions willbe an atmosphere comprising a mixture of hydrogen and hydrogen sulfide.It is also preferred that the support material comprise a suitableinorganic refractory oxide.

In the embodiment where the promoter metal consists of iron, acomposition of this invention can also be obtained by heating, underoxygen-free conditions (and preferably in the presence of excess sulfur)at a temperature of at least about 200° C. for a time sufficient to formsaid catalyst, a composite of inorganic refractory oxide supportmaterial and a mixture of (i) a hydrated oxide of trivalent chromium and(ii) a thiometallate salt of the general formula FeL(MoS₄), FeL(WS₄) andmixtures thereof, wherein L is as defined above. Again, in a preferredembodiment, ligand L will be three bidentate or two tridentate chelatingamines and the oxygen-free conditions will be an atmosphere comprising amixture of hydrogen and hydrogen sulfide.

Hydroprocessing catalyst is meant to include catalysts useful for anyprocess that is carried out in the presence of hydrogen, including, butnot limited to, hydrocracking, hydrodenitrogenation,hydrodesulfurization, hydrogenation of aromatic and aliphaticunsaturated hydrocarbons, methanation, water gas shift etc. Thesereactions include hydrotreating and hydrorefining reactions, thedifference generally being thought of as more of a difference in degreethan in kind, with hydrotreating conditions being more severe thanhydrorefining conditions. Some of the catalysts of this invention havebeen found to have hydrotreating or hydrorefining activitiessubstantially greater than that of catalysts derived from conventionalhydrotreating catalyst precursors such as cobalt molybdate on alumina,even though their surface areas are not as high.

DETAILED DESCRIPTION OF THE INVENTION

The precise nature and composition of the catalyst species that isformed as a result of heating the composite of precursor and supportmaterial in the presence of sulfur and under oxygen-free conditions isnot known. The composition of the corresponding unsupported catalystspecies is defined in U.S. patent application Ser. No. 656,144 jointlyfiled by A. J. Jacobson, T. C. Ho, R. R. Chianelli, J. J. Steger and A.A. Montagna on even date herewith. Unlike applicants' species, however,the catalyst species of Jacobson et al. are unsupported, bulk catalysts.They thus differ from the supported catalyst species defined herein. Thecatalyst species of this invention achieve superior utilization of thecatalytic material.

The bulk, unsupported catalyst species defined in co-pending Ser. No.656,144 are unique in that they exist as a single phase of amorphousmetal sulfide. These compositions comprise a non-crystalline amorphousmetal sulfide phase of trivalent chromium with Mo and/or W. As statedabove, these compositions may also contain one or more promoter metalsselected from the group consisting of Fe, Ni, Co, Mn Mn, Cu, Zn andmixtures thereof, preferably Fe, Ni, Co, Mn and mixtures thereof. Thus,by way of illustrative, but non-limiting examples, these bulk,unsupported compositions include a single phase, amorphous, metalsulfide of (i) trivalent chromium and Mo; of (ii) trivalent chromium, Moand divalent Ni; (iii) of trivalent chromium, W, Mo, and Ni and Fe, etc.

By amorphous is meant a compound which exhibits no detectablecrystallinity when measured by X-ray diffraction (XRD), an analyticaltechnique well-known to those skilled in the art. Thus, bulk unsupportedspecies analyzed by XRD have exhibited no detectable crystallinity.Further, bulk, unsupported species analyzed by high resolution scanningtransmission electron microscopy (HREM) with a microscope having a 4 Åpoint-to-point resolution revealed the absence of any crystallinematerial 15 Å or more in the largest dimension, 15 Å being about thelimit of detectability with such an instrument.

In one method of preparing the catalyst species of this invention, aslurry of precursor salt, or mixture of salts, is incorporated with apreselected quantity of refractory inorganic oxide support material,preferably a particulate mass of said support, with the salt-containingsupport or composite of salt and support then dried. The dried compositeof salt and support is then heated in an oxygen-free atmosphere in thepresence of sulfur or sulfur-bearing compound at elevated temperature toform the catalyst species of this invention. A sufficient amounts of thesalt, or salts, is composited with the support so that prior to, or atthe time that the composite of support and precursor salt or salts isheated in the presence of sulfur and hydrogen and under oxygen-freeconditions, generally from about 10 weight percent to about 25 weightpercent of the salt, expressed as weight of MoO₃ or WO₃ on an ignitionloss free basis, will be present on the support. The supported catalystspecies of this invention are suitable, highly active and selective ashydrotreating catalysts.

The catalyst support will typically be a particulate, porous inorganicrefractory oxide in the form of beads, pills, pellets, sieved particles,extrudates, or the like in dry or solvated state which is contacted witha slurry of precursor. Alternatively, the supported catalyst species ofthis invention are formed by forming the precursor in the presence of aslurry of colloidal or non-colloidal particles of support material.Typical support materials include alumina, diatomaceous earth, zeolite,silica, activated carbon, magnesia, zirconia, boria, chromia, titaniaand the like. A preferred support for the practice of the presentinvention is one having a surface area of more than 50 m² /g, preferablyfrom about 100 to 300 m² /g.

A preferred method for preparing the composite of precursor salt andsupport that forms the catalyst precursor of this invention is toprepare the precursor salt in the presence of a colloidal ornon-colloidal slurry of particles of support material. Thus, thecatalyst precursor composite may be formed by contacting, in thepresence of an aqueous slurry of particles of support material, one ormore thiometallate salts of Mo, W or mixtures thereof, in the presenceof one or more ligands L, with one or more chelated, promoter metalcations containing trivalent chromium of the general formula [Cr_(1-z)M_(z) LX_(y) ]^(2n+) for a time sufficient to precipitate said precursorfrom said solution. The chelated, water soluble trivalent chromiumcontaining cation is formed under anhydrous conditions by dissolving asoluble salt of trivalent chromium in a mixture of one or more ligands,L, at low temperature, followed by heating said solution to atemperature sufficient to precipitate a chelated trivalent chromiumcation and then contacting (if one or more promoter metals is desired inthe catalyst), in aqueous solution, and so-formed chelated, trivalentchromium cation with one or more water soluble salts of chelated,divalent promoter metal. If only iron is desired as a promoter metal,the catalyst precursor can be formed by contacting an aqueous slurry ofparticles of hydrated oxide of trivalent chromium formed in situ from asoluble trivalent chromium salt or added as such with a water-soluble ofdivalent iron in the presence of one or more ligands, L and one or moresoluble thiometallate salts of Mo, W or mixture thereof in the presenceof a slurry of particles of one or more support materials. It should benoted that an excess of chromia will result in the formation of acatalyst composite wherein chromia forms the support or part thereof,depending on whether or not other support material is present.

As set forth above, the compositions of this invention will be formed byheating, at elevated temperature and in the presence of sulfur, acomposite of inorganic refractory oxide support material and one or moreprecursor salt compounds wherein said precursor salt is selected fromthe group consisting of [Cr_(1-z) M_(z) LX_(y) ][MoS₄ ]_(n), [Cr_(1-z)M_(z) LX_(y) ][WS₄ ]_(n) wherein n=(3-z-y)/2 and mixtures thereofwherein M is one or more divalent promoter metals selected from thegroup consisting of Mn, Fe, Co, Ni, Cu, Zn and mixtures thereof.Preferably M will be selected from the group consisting of divalent Fe,Ni, Co, Mn and mixtures thereof. In the above formulae, 1>z≧0 and1-z≧y≧0, L is one or more neutral nitrogen-containing ligands, at leastone of which is a chelating polydentate ligand, and X is a singlycharged anionic ligand. Thus, if no divalent promoter metal and noanionic ligand is present, n will be equal to 1.5 If one or moredivalent promoter metal ions such as Ni, Fe, Co, etc. are present, thenn will be less than 1.5 but will usually be greater than 1.0 due to thepresence of the trivalent chromium ion, with the actual value of ndepending on the relative amounts of trivalent chromium and divalentmetal ions. In all cases where y=1-z then n=1.

Thus, the catalyst precursor salt must contain trivalent chromium (Cr³⁺)in addition to Mo, W or mixture thereof. If no divalent promoter metalsare present, the precursor salt will have the formula (CrL)(MoS₄)₁.5 ifmolybdenum is present in the anion and (CrL)(WS₄)₁.5 if tungsten ispresent in the anion. Alternatively, the precursor salt may contain adivalent promoter metal or a mixture of two, three, four, five or evensix promoter metals. For the case of one promoter metal, such asdivalent metal Co²⁺ and in the absence of an anionic ligand X (y=0), amolybdenum containing precursor salt will have the formula [(Cr_(1-z)Co_(z) L](MoS₄)_(n) wherein 0<z<1. In the case of two promoter metalssuch as Ni²⁺ and Co²⁺, the precursor will have the formula of the form[(Cr_(1-z) Ni_(z') Co_(z"))L](MoS₄)_(n) wherein z=z'+z", and 0<z<1, etc.It is understood of course that a mixture of precursor salts may beused.

As defined above, ligand L will be one or more neutral, nitrogencontaining ligands wherein at least one of said ligands is amultidentate chelating ligand, and ligand X is a singly charged anionicspecies. Ligands L and X coordinate to the metal cation to form acomplex metal cation [Cr_(1-z) M_(z) LX_(y) ]^(2n+). Thus, for the caseof i.e., molybdenum, the thiometallate anion (MoS₄)²⁻ will be ionicallybound to the above complex metal cation.

Those skilled in the art know that the term "ligand" is used todesignate functional coordinating groups which have one or more pairs ofelectrons available for the formation of coordinate bonds. Ligands thatcan form more than one bond with a metal ion are called polydentatewhile ligands that can form only one bond with a metal ion are calledmonodentate ligands are not capable of forming chelates. Hence, if oneuses one or more species of monodentate ligands in the precursormolecule, then one must also use at least one polydentate chelatingligand. Preferably L will be one or more polydentate chelating ligands.The total denticity of the ligand species comprising L will besufficient to satisfy the coordination requirements of the promotermetals. This requirement will usually lead to a total denticity of six.

Thus, in the absence of any anionic ligands, i.e. when y=0, L will bethree bidentate ligands, two tridentate ligands, a mixture of abidentate and a quadridentate ligand, a hexadentate ligand or a mixtureof a polydentate ligand with monodentate ligands as long as thecombination has a total denticity of about six. As has heretofore beenstated, it is preferred to use chelating bidentate and tridentatealkylamine ligands. In general, the ligands useful in this inventioninclude alkyl and aryl amines and nitrogen heterocycles. Illustrativebut non-limiting examples of ligands useful in the catalyst precursorsof this invention are set forth below.

Monodentate ligands will include NH₃ as well as alkyl and aryl aminessuch as ethylamine, dimethyl amine, aniline and nitrogen heterocyclicamines such as pyridine, etc. Useful chelating bidentate amine ligandare illustrated by ethylenediamine, 2,2'-bipyridine, o-phenylenediamine, tetramethylethylenediamine and propane-1,3 diamine. Similarly,useful chelating tridentate amine ligands are represented by terpyridineand diethylenetriamine while triethylenetetramine is illustrative of auseful chelating quadridentate amine ligand. Useful chelatingpentadentate ligands include tetraethylene pentamine while sepulchrate(an oxtazacryptate) is illustrative of a suitable chelating hexadentateligand. As a practical matter it will be preferred to use chelating,polydentate alkyl amines for L. Illustrative, but not limiting examplesor alkyl amines that are useful in the catalyst precursor of thisinvention include ethylenediamine (en), diethylenetriamine (dien), andtetraethylenetetramine. It is particularly preferred to use bidentateand tridentate alkyl amines such as ethylenediamine anddiethylenetriamine.

As defined above, ligand X is a singly charged anionic species, such asNO₂ ⁻, OH⁻, etc. It is always present in conjunction with the neutralnitrogen-containing ligand L in amounts given by 1-z≧y≧0 in the generalformula previously defined. Even when X is present, at least one ofligands L must be a chelating polydentate ligand. The sum of L and Xmust still satisfy the coordination requirement, usually six, of thepromoter metals. Therefore, since y cannot exceed unity, the anionicligand can at most satisfy one of the six coordination requirements ofthe promoter metal.

The value of y affects the Cr/Mo (or Cr/W) ratio in the precursorcompound. Thus, when y=1, and there is no divalent promoter metal (z=0),the Cr/Mo ratio is 1/1. When z≠0, such as z=0.5, as will be the case ifsome Ni or Co, for example, are present, and if y=0.5, then the Cr/Moratio is 1/2, etc.

Thus, it will be appreciated that because the value of n may varybetween 1.5≧n≧1.0 depending on (a) the amount, if any, of divalentpromoter metal M present in the cation, and (b) the amount, if any, ofthe anionic ligand X, the theoretical ratio of the trivalent chromiumplus promoter metal (if any) to molybdenum and tungsten in a compositionof this invention formed from a single precursor salt species will vary,from 1/1 to 1/1.5.

Some of the precursor salts useful in forming the catalysts of thisinvention and methods for preparing them are known in the art althoughit has not heretofore been known that such salts can be useful catalystprecursors. An article by Diemann and Mueller titled" Thio and SelenoCompounds of the Transition Metals With d° Configuration" published inCOORD. CHEM. REV. 10:79-122 provides a review of some such known salts,including salts with neutral nitrogen containing ligands of type L, withcombinations of ligands of type L and singly charged anionic ligands ofthe type X.

In general however, the precursor compounds useful for forming thecompositions of this invention may be prepared by mixing a solution ofan appropriate thiometallate such as ammonium thiomolybdate and/orthiotungstate in a mixture of ligand(s) L and water with an aqueoussolution of the chelated promoter metal cation, containing trivalentchromium [Cr_(1-z) M_(z) LX_(y) ]^(2n+), which results in the formationof the precursor compound as a precipitate which is readily recovered.The chelated, trivalent chromium containing cation is formed underanhydrous conditions by dissolving a soluble salt of trivalent chromium,such as CrCl₃, in an appropriate ligand or ligand mixture at lowtemperature (i.e., 0° C.). When this solution is warmed up to, i.e.,ambient temperature, the chelating reaction occurs and the chelated saltprecipitates. The product can be filtered, washed with methanol anddried for subsequent use. The chelated divalent metal promoter cation iseasily formed by, for example, mixing an aqueous solution of one or morewater soluble promoter metal salts with the ligand. The water solublesalt may be any water soluble salt that is convenient to use such as ahalide, sulfate, perchlorate, acetate, nitrate, etc. While the chelatedsalts are generally water soluble, they can be precipitated from theiraqueous solutions by the addition of methanol, filtered and washed withmethanol, and dried. For example, solid Ni(en)₃ Cl₂ can be prepared byadding ethylenediamine (en) to an aqueous solution of NiCl₂.6H₂ O,adding methanol to precipitate the chelate, washing with methanol anddrying.

The anhydrously prepared chelated chromium cation salt is dissolved inwater along with the chelated divalent promoter salt. The ammoniumthiometallate solution is mixed with this solution containing thechelated promoters, resulting in the precipitation of the catalystprecursor salt. The precursor salt will preferably be formed in thepresence of a slurry or colloidal suspension of support material. Theprecursor compound preparation will be further understood by referenceto the Examples, infra.

The difference in the method of preparing the chelated chromium promotercation from the chelated divalent metal promoter cations is the factthat chromium chelation is slow compared to that of the divalent ions.As a result, the addition of the basic ligand to an aqueous chromiumsalt solution will result in the formation predominantly of hydratedchromium oxide instead of the chelate (CrL)Cl₃. To avoid this hydratedoxide formation, the chromium chelation is carried out under anhydrousconditions by adding the trivalent chromium salt to the dry ligand. Onecan prepare the divalent promoter metal chelates in the same manner,either separately or along with the trivalent chromium chelates.

However, in an embodiment where the divalent promoter metal consistsonly of iron, it is not necessary to maintain anhydrous conditionsduring the addition of the ligand to the chromium salt solution. Thus,precursor salts useful for forming iron containing compositions of thisinvention may be prepared by mixing an aqueous slurry of (i) hydratedoxide of trivalent chromium Cr(OH)₃.xH₂ O with (ii) iron and ligandcontaining thiometallate salts and, optionally, (iii) one or morethiometallate salts containing the conjugate acid of one or more ligands(but no divalent promoter metal) precipitating the thiometallate saltonto the slurried particles of hydrated chromium oxide and recoveringthe precursor. The hydrated chromium oxide may be freshly precipitatedfrom an aqueous solution of a trivalent chromium salt. Alternatively,the source of hydrated chromic oxide may be a colloidal, aqueoussuspension of same. These materials are commercially available and havebeen found useful in forming the compositions of this invention. In onemethod of preparation, the hydrated chromium oxide will be precipitatedfrom an aqueous solution of trivalent chromium salt by contacting saidsalt solution with one or more basic amine chelating agents. Again,however, these precursors are preferably formed in the presence of asuitable support material, including chromia or chromia coated materialsin which case one will obtain a composite of support material andprecursor.

The compositions or catalysts of this invention may be prepared byheating a composite of support material and one or more precursor saltsin an oxygen-free environment, in the presence of sulfur, at atemperature of at least about 200° C. for a time sufficient to form thecatalyst. Although the sulfur required during the formation of thecatalyst may be present in the precursor, it is preferred that sulfur bepresent in an amount in excess of that contained in the precursor. Thus,it is preferred that the composition of this invention be formed byheating the precursor in the presence of sulfur or, preferably, in thepresence of a sulfur bearing compound. Mixtures of hydrogen and H₂ Shave been found to be particularly suitable. Preferably the temperaturewill range between from about 250°-600° C., more preferably from about250°-500° C. and still more preferably from about 300°-400° C. Theoxygen-free conditions may be gaseous, liquid or mixture thereof.

The compositions of the bulk, unsupported species of Jacobson et alcorresponding to the supported species of this invention wereestablished using a number of analytical techniques briefly describedbelow.

X-ray diffraction (XRD) analysis was done by grinding a sample to finepowder and packing it into an alumina tray containing a cylindricalrecess 25 mm in diameter and 1 mm in depth. The top surface of thesample was flat and co-planar with the top of the aluminum tray afterthis preparation. Measurements were made in ambient atmosphere using aSiemens D500 X-ray diffractometer in 0-20 reflection (Bragg-Brentano)geometry. The incident X-ray beam was taken from a fixed anode coppertarget with a wavelength of 1.54178 Å. The diffracted beams weremonochromated using a graphite monochromator to minimize fluoresence andwere detected using a proportional counter detector. Data were collectedby stepping the detector in angular increments of 0.020°20 and countingat each step for two seconds. The intensity and angular information werestored in a PDP 1103 computer and subsequently plotted as detectedcounts in 2 seconds versus 20.

The morphology and crystal structure determination of the constituentphases of the bulk, unsupported catalyst species of Jacobson, et al.were carried out using high resolution and analytical electronmicroscopy. In this procedure, described in P. C. Flynn et al., J.Catal., 33, 233-248 (1974), the transition metal sulfide powder isprepared for the Transmission Electron Microscope (TEM) by crushing inan agate mortar and pestle to produce powder fragments through which anelectron beam can pass. The crushed powder is ultrasonically dispersedin hexane and a drop of this suspension is allowed to dry onto astandard 3 mm TEM grid, which is covered with a thin (≦200 Å) amorphouscarbon film. Samples were analyzed in a Philips 400T FEG TEM at 100 KVby bright field imaging, energy dispersive X-ray microanalysis, andmicrodiffraction.

Quantitative chemical analysis was obtained by the thin foil ratiomethod, as described in G. Cliff and G. W. Lovimer; J. Microscopy, 1975,Volume 103, Page 203, and absorption effects were analyzed and correctedusing the procedure described by Goldstein, et al. in "Introduction toAnalytical Electron Microscopy", J. J. Hren, J. I. Goldstein, and D. C.Joy eds, Plenum Press, New York, NY 1979, Page 83. X-ray fluorescentspectra was generated from the excited volume of a sample defined by acylinder of 100 Å probe size and the thickness of the sample (typically1000 Å).

An additional method used to evaluate the extent of dispersion andchemical state of the bulk, unsupported metal sulfide catalyst speciesof Jacobson et al. was EXAFS (Extended X-ray Absorption Fine Structure).EXAFS is an element-specific electron scattering technique in which acore electron ejected by an X-ray photon probes the local environment ofthe absorbing atom. The ejected photoelectron is backscattered by theneighboring atoms of the absorbing species and interferes constructivelyor destructively with the outgoing electron wave, depending on theenergy of the photoelectron. The energy of the photoelectron is equal tothe difference between the X-ray photon energy and a threshold energyassociated with ejection of the electron. In the EXAFS experiment, thephotoelectron energy is varied by varying the energy of the incidentX-ray beam. The interference between outgoing and backscattered electronwaves as a function of energy modulates the X-ray absorption coefficientso that the EXAFS function K.X(K) is observed experimentally asoscillations in the absorption coefficient ( ) on the high energy sideof the absorption edges (c.f. Via et al., J. Chem. Phys., 71, 690(1979).

As discussed under Background of the Disclosure, molybdenum and tungstensulfide catalysts have many uses, including hydrotreating. As shown inthe following Table, hydrotreating conditions vary considerablydepending on the nature of the hydrocarbon being hydrogenated, thenature of the impurities or contaminants to be reacted or removed, and,inter alia, the extent of conversion desired, if any. In general,however, the following are typical conditions for hydrotreating anaphtha boiling within a range of from about 25° C. to about 210° C., adiesel fuel boiling within a range of from about 170° C. to 350° C. aheavy gas oil boiling within a range of from about 325° C. to about 475°C., a lube oil feed boiling within a range of from about 290° to 550°C., or residuum containing from about 10 percent to about 50 percent ofa material boiling above about 575° C.

    ______________________________________                                        Typical Hydrotreating Conditions                                                                           Space  Hydrogen                                                     Pressure  Velocity                                                                             Gas Rate                                  Feed     Temp., °C.                                                                       psig      V/V/Hr SCF/B                                     ______________________________________                                        Naphtha  100-370   150-800    0.5-10                                                                              100-2000                                  Diesel Fuel                                                                            200-400   250-1500  0.5-4  500-6000                                  Heavy Gas                                                                              260-430   250-2500  0.3-2  1000-6000                                 Oil                                                                           Lube Oil 200-450   100-3000  0.2-5    100-10,000                              Residuum 340-450   1000-5000 0.1-1   2000-10,000                              ______________________________________                                    

It should be noted that the catalysts of this invention are also usefulin lube oil refining processes where it is desirable to remove oxidationinitiating nitrogen compounds from lube oil feeds.

The invention will be further understood by reference to the followingexamples.

EXAMPLES EXAMPLE 1 Preparation of Catalyst Precursor A of Formula[Cr(en)₃ ](MoS₄)₁.3

In this experiment, a catalyst precursor of the formula [Cr(en)₃](MoS₄)₁.3 was prepared according to the following procedure. First,[Cr(en)₃ ]Cl₃ was prepared under anhydrous conditions in order to avoidor minimize the formation of chromium hydroxide. Thus, 150 ml ofethylenediamine (en) was cooled to ice bath temperature. To this wasadded 20 g of anhydrous CrCl₃ in small aliquots, allowing each aliquotaddition to be well mixed into the en before adding the next addition inorder to prevent too much heat from being generated from the reaction ofCrCl₃ with the en. After all the CrCl₃ had been added to the en, themixture was warmed up to room temperature, which resulted in [Cr(en)₃]Cl₃ being formed as a yellow precipitate. In order to insure completereaction, the slurry was continuously stirred for another four hours.The yellow product was filtered, thoroughly washed with methanol anddried at reduced pressure under dry nitrogen to yield approximately 42grams of [Cr(en)₃ ]Cl₃ of 98 percent purity.

Thirty-four g of the yellow [Cr(en)₃ ]Cl₃ was then dissolved in 450 mlH₂ O which formed a cloudy solution. This solution was filtered in orderto obtain a clear solution. Next, 25.7 g of (NH₄)₂ MoS₄ was dissolved in150 ml en and cooled in an ice bath. The [Cr(en)₃ ]Cl₃ solution wasadded to the (NH₄)₂ MoS₄ solution with stirring which resulted in theformation of a bright, orange-red precipitate. The resulting slurry wasstirred for an extra thirty minutes. The orange-red precursor productwas filtered, washed with methanol and also dried at reduced pressureunder nitrogen to yield 41 grams of the Precursor A having the generalformula [Cr(en)_(3-y/2) (OH)_(y) ](MoS₄).sub.(3-y)/2 where y isapproximately 0.5. Elemental analysis of the catalyst precursor productare set forth in the table below.

EXAMPLE 2 Preparation of Catalyst Precursor B of Formula [Cr(en)₃](MoS₄)₁.6

Because the atomic ratio of Cr to Mo was not 1/1.5, another batch ofprecursor, Precursor B was made using a sample of recrystallized[Cr(en)₃ ]Cl₃. Precursor B on elemental analysis was found to have achrome to molybdenum ratio of slightly higher than 1/1.5, but within theexperimental error of the analysis. These results are also set forth inthe table below.

    ______________________________________                                                Cr  Mo     S      N    C    H   O   Mo/Cr                             ______________________________________                                        Precursor A                                                                             9.6   22.4   30.5 15.8 13.7 5.0 3.1 1.3 ± .1                     Precursor B                                                                             8.4   24.8   33.6 14.7 12.6 4.2 1.9 1.6 ± .1                     ______________________________________                                    

An infrared spectrum of Precursor A did not show a characteristicabsorption near 1600 cm⁻¹ which would have indicated the presence ofwater of hydration. Instead, there were some peaks below 1200 cm⁻¹ whichcould have been due to hydroxy complexes as expressed in the abovegeneral formula, and as indicated by the presence of oxygen in theelemental analysis. Kazuo Nakamoto in "Infrared and Raman Spectro ofInorganic and Coordination Compounds", J. Wiley & Sons, 1978 states onp. 229 that "the hydroxy group can be distinguished from the aquo groupsince the former lacks the HOH bending mode near 1600 cm⁻¹ [. . . in theinfrared spectrum . . . ]. Furthermore, the hydroxy complex exhibits theMOH bending mode below 1200 cm⁻¹."

EXAMPLE 3 Preparation of Catalyst Precursor C [Cr₀.5 Fe₀.5 (en)₃](MoS₄)₁.25

In another experiment, a catalyst precursor (Precursor C) of the formula[Cr₀.5 Fe₀.5 (en)₃ ](MoS₄)₁.25 was prepared by the following procedure.First, the amine thiomolybdate of ethylenediamine (en) was prepared bydissolving 31.3 g of (NH₄)₂ MoS₄ in 100 ml of en which had been degassedwith nitrogen and cooled in an ice bath. From this point on, alloperations were carried out under N₂ except during the work-up of theproduct. [Cr(en)₃ ]Cl₃, as prepared above, was dissolved in water andfiltered to produce 150 ml of solution containing 16.4 g of the chelatedsalt. To this solution, 9.64 g of FeCl₂.4H₂ O was added, resulting in abrownish suspension. This suspension was slowly added to the cooled(NH₄)₂ MoS₄ solution with vigorous agitation. Thirty minutes afteraddition was complete, the orange-red precipitated product was filteredunder anaerobic conditions. It was washed with a mixture of 200 ml H₂ Oand 20 ml en, followed by 3 washes with methanol, 200 ml each and driedby vacuum suction under N₂ overnight. The yield of Precursor C wasapproximately 45 g.

EXAMPLE 4 Preparation of Catalyst Precursor D [Cr₀.5 Ni₀.5 (en)₃](MoS₄)₁.25

In the following experiment, a nickel containing catalyst precursor(Precursor D) of the formula [Cr₀.5 Ni₀.5 (en)₃ ](MoS₄)₁.25 was preparedaccording to the following procedure. First, 31.38 g. of (NH₄)₂ MoS₄ wasdissolved in 100 ml degassed en and cooled in an ice bath. Previouslyprepared [Cr(en)₃ ]Cl₃ (16.4 g) and 16.7 g of [Ni(en)₃ ]Cl₂, synthesizedin the conventional manner by methanol precipitation from an aqueoussolution of NiCl₂.6H₂ O to which en had been added, were dissolved in amixture of 150 ml water and 5 ml en. This solution was filtered. Theclear filtrate was added dropwise to the (NH₄)₂ MoS₄ solution withvigorous agitation. A red-orange precipitate formed. After addition wascompleted, the red-orange product was filtered. It was washed with amixture of 450 ml H₂ O and 60 ml en in 3 washes, followed by a 300 mlmethanol wash, and a 100 ml diethylether wash. After vacuum drying, theyield of Precursor D was approximately 45 g.

EXAMPLE 5 Preparation of Another Chromium-Iron Thiomolybdate CatalystPrecursor E

A chromium-iron thiomolybdate catalyst precursor was prepared bydissolving 40 gm of (NH₄)₂ MoS₄ into 86 ml of ethylenediamine (en) in aone liter flask. Distilled H₂ O was used twice to wash off any solutionremaining on the sides of the flask. The resulting dark red solution wascooled to 0° C. in a wet ice bath and kept in the bath for the durationof the experiment. In a separate flask a mixture of 16.52 gm CrCl₃.6H₂ Oand 12.36 gm FeCl₂.4H₂ O was dissolved into 250 ml of distilled waterand 25 ml of ethylenediamine was added which formed a precipitate. Thisslurry was then allowed to stand for 2-3 hours after which it was addeddropwise, to the aqueous (NH₄)₂ MoS₄ /en solution with agitation. Anorange precipitate formed and the mixture was stirred in the ice bathfor one half hour after the additon was completed. The precipitate wasseparated out by vacuum filtration, washed with ethanol and dried undervacuum for 16-24 hrs. at room temperature. Seventy-nine grams ofprecipitate, Precursor E, were recovered.

EXAMPLE 6 Preparation of Another Fe-Cr Thiomolybdate Catalyst PrecursorF

Another chromium-iron promoted thiomolybdate catalyst precursor wasprepared in a similar manner by dissolving 40 grams of (NH₄)₂ MoS₄ in 82ml of diethylenetriamine (dien) in a 1 liter flask. Distilled water wasused to wash off any solution remainng on the sides of the flask and theresulting dark red solution was cooled to 0° C. in a wet ice bath andkept in the bath for the duration of the experiment. In a separate flaska mixture of 12.36 grams of FeCl₂.4H₂ O and 16.52 grams of CrCl₃.6H₂ Owere dissolved in 250 ml of distilled water and 25 ml ofdiethylenetriamine was added to form a precipitate. This slurry wasallowed to stand for 2-3 hours after which it was added dropwise to the(NH₄)₂ MoS₄ /dien solution with agitation. A bright orange precipitateformed. The resulting precipitate/solution was stirred in the ice bathfor a half hour after the reaction was completed. The precipitate wasthen separated by vacuum filtration and washed with water and ethanoland then dried under vacuum. Eighty-three grams of orange coloredprecipitate, Precursor F, were recovered.

EXAMPLE 7 Preparation of Catalyst Precursor G Using Excess ColloidalChromia

A catalyst precursor containing iron, molybdenum and chromium wasprepared according to the following procedure employing excess amountsof chromia.

An aqueous chromia sol was obtained from Nyacol containing 22 wt.% ofCr₂ O₃ particles having an average particle size of about 50 Å. An 80.7gm sample of this sol (containing 0.117 mole Cr₂ O₃) was added to alarge three-neck, round-bottom flask, and diluted to a total volume of400 ml with deionized water. To this colloidal suspension was added 11.5gms of (0.029 mole) of Fe(NH₄)₂ (SO₄)₂.6H₂ O dissolved in 50 ml. ofdeionized water. Upon addition of the ferrous ammonium sulfate solution,the colloidal chromia gelled. The gel was vigorously stirred by means ofan air-driven stirrer. At this point, 7.6 gms. (0.029 mole) of ammoniumthiomolybdate [(NH₄)₂ MoS₄ ] dissolved in a mixture of 25 ml.ethylenediamine and 100 ml. water was slowly added to the stirred gel.This caused the formation of a precursor of a composition of thisinvention which was a brown-black precipitate of trisethylenediamineiron (II) thiomolybdate admixed with the chromia. Thus, the flaskcontained iron, molybdenum and chromium, respectively, in the atomicratios of 1:1:8. The precursor precipitate was recovered by vacuumfiltration and dried in vacuum at 50° C. for 24 hours, yieldingPrecursor G containing about 50% Cr₂ O₃.

EXAMPLE 8 Preparation of Supported Catalyst Precursor H

In this experiment, an iron promoted chromium-molybdenum catalystprecursor supported on silica was prepared. Colloidal silica, 49.7 gms,containing 34 wt.% SiO₂ was put into a large flask and diluted withdeionized water to 400 ml. An aqueous solution of 5.4 g Fe(NH₄)₂(SO₄)₂.6H₂ O and 5.5 g Cr(NO₃)₃.9H₂ O in 50 ml water was added to theabove suspension with stirring. A solution of 8.9 g of (NH₄)₂ MoS₄ in100 ml H₂ O and 25 ml of en was then added, dropwise, to the flask withvigorous stirring. The resultant precipitate was filtered, washed anddried to yield 31 g of Precursor H.

EXAMPLE 9 Catalyst Preparation

For these experiments, the catalyst precursors of Experiments 1-8 werepelletized using a 4% aqueous solution of polyvinyl alcohol as a binderand then were placed into a stainless steel reactor, heated to 100° C.at atmospheric pressure and purged for one hour with nitrogen. Tenpercent of hydrogen sulfide in hydrogen was introduced into the reactorat a rate of 0.75 SCF/hr for each 10 cc of catalyst in the reactor. Thetemperature in the reactor was then raised to 325° C. and kept at thistemperature for three hours to form the catalyst after which thetemperature in the reactor was lowered to 100° C., the H₂ S/H₂ gas flowwas stopped and the reactor was purged with nitrogen until roomtemperature was reached.

EXAMPLE 10 Characterization of Catalyst Derived From Catalyst PrecursorA (Example 1)

X-ray diffraction analysis of the catalyst composition derived fromcatalyst precursor A revealed no evidence of any crystalline phases.Particularly, there was no "002" peak near 2θ=12° which would indicatemultilayer stacking typical of molybdenum sulfide-like compositions.This finding corroborates the evidence of the HREM micrograph, to bediscussed below. X-ray diffraction analysis of catalyst compositionsobtained from Precursors C and D also showed no evidence ofcrystallinity or the presence of molybdenum sulfide-like layer materialwhich would give rise to a (002) peak.

An X-ray diffractions pattern was also run on the lined outchromium/molybdenum sulfide catalyst derived from Precursor A. The dataindicated little crystallinity and a small indication of a 002 peakbetween 2θ values of 10° and 15°, indicative of some molybdenumsulfide-like layer formation.

The catalyst derived from precursor A was examined and analyzed by HREMand was found to be amorphous. Chemical analysis carried out in theelectron microscope indicated a chemically homogeneous single phasewithin the 100 Å spatial resolution of the analysis. The chemicalcomposition was determined as a 1/1 ratio of Cr/Mo within the ±20%precision of the technique.

Some double lines were found in the electron photomicrographs which,while not wishing to be held to any particular theory, are believed tohave been very tiny crystallites or crystal material about 6 Å thick ofa molybdenum sulfide-like phase. The absence of any observablecrystallinity using this HREM technique implies that if crystallites doexist in the bulk, amorphous material, then they must be less than about15 Å thick in their largest dimension, due to the fact that this isabout the limit of detectability using the HREM method. Again, while notwishing to be held to any particular theory, it is believed that small,plate-like crystallites of a general molybdenum sulifde structure mayexist within the bulk amorphous material. It should be known that evenif the bulk, amorphous material were completely composed of tiny, smallplate-like crystallites, such a composition would still appear to beamorphous when analyzed by HREM using the present resolution. Thus,whether a material is crystalline or amorphous and, if so to whatextent, can be and sometimes is a matter both of definition and of thetechnique or techniques used to measure crystallinity.

EXAFS data of the chromium/molybdenum composition derived from PrecursorA indicated that the amorphous structure of the composition extends downto the local atomic structure with no detectable phase separation.

EXAMPLE 11

Chemical analyses were run on the catalyst compositions derived from thePrecursors A, F and G. The results of these analyses for A and F areshown in the Table below.

ELEMENTAL ANALYSIS (WT.%) OF COMPOSITIONS DERIVED FROM PRECURSORS A ANDF

    ______________________________________                                        Precursor                                                                             Cr      Fe     Mo    N    C     H    S                                ______________________________________                                        A       14.40   --     34.10 2.55 4.44  1.32                                  F        5.07   10.63  21.81 5.07 9.59  1.73 26.31                            ______________________________________                                    

The catalyst prepared from Precursor G (Example 7) gave the followingelemental analysis: Fe, 3.03 wt.%, Mo, 5.09; Cr, 23.0. This yields anFe/Mo/Cr atomic ratio of 1.0/0.98/8.1.

X-ray diffraction analysis of catalysts prepared from precursors E and Frevealed no evidence of any crystalline phases.

EXAMPLE 12 Catalyst Evaluation

The catalysts were loaded into a fixed-bed reactor. The conditions inthe reactor were as set forth below:

Temperature: 235° C.

Pressure: 3.15 MPa, 6.0 MPa

Hydrogen Rate: 3000 SCF/bbl

LHSV: 3.0 V/V/Hr

The liquid product was analyzed for total sulfur by X-ray fluorescenceand for nitrogen by combustion analysis. The feedstock used was a lightcatalytic cycle oil (LCCO) that was about 20 wt.% paraffinic havingproperties set forth in Table 1.

In all of these experiments, the results obtained from the catalysts ofthis invention were compared to results obtained from a commercialhydrotreating catalyst precursor comprising nickel molybdate on γ-Al₂O₃. This material contained 18 percent molybdenum oxide and 3.5 percentnickel oxide supported on a gamma alumina. These commercial precursorswere sulfided employing the same procedure used to form the catalysts ofthis invention, except that the temperature was held at 360° C. for onehour.

The results of these experiments are shown in Tables 2 through 8 andshow that the catalysts of this invention are not only usefulhydrotreating catalysts but have higher selectivity forhydrodenitrogenation than the commercial nickel molybdate on aluminacatalyst.

                  TABLE 1                                                         ______________________________________                                        LCCO Feed                                                                     Gravity (°API)                                                                         18.6                                                          Sulfur, wt. %    1.4                                                          Nitrogen, ppm   292                                                           ______________________________________                                        GC Distillation                                                               Wt. %           Temp., °C.                                             ______________________________________                                         5              231                                                           10              251                                                           50              293                                                           70              321                                                           90              352                                                           95              364                                                           ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Hydrotreating Activity for Catalyst Derived from                              Commercial Nickel Molybdate on Alumina, at 3.15 MPa                           Catalyst Hours                                                                On Stream       % HDS    % HDN                                                ______________________________________                                        49              80.0     32.3                                                 71              80.8     38.6                                                 75              80.0     37.6                                                 ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Hydrotreating Activity for Catalyst Composition                               Derived From Precursor A, at 3.15 MPa                                         Catalyst Hours                                                                on Stream       % HDS    % HDN                                                ______________________________________                                        41              35.1     46.9                                                 62              39.6     48.0                                                 109             42.3     54.2                                                 ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Hydrotreating Activity for Catalyst                                           Composition Derived From Precursor C                                          Catalyst Hours                                                                            Reactor                                                           on Stream   Pressure MPa % HDS    % HDN                                       ______________________________________                                        23          3.15         31.6     33                                          44          6.0          38.2     54.2                                        ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Hydrotreating Activity for Catalyst                                           Composition Derived From Precursor D                                          Catalyst Hours                                                                            Reactor                                                           on Stream   Pressure MPa % HDS    % HDN                                       ______________________________________                                        23          6.0          87.5     94.5                                        ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Hydrotreating Activity For Catalyst Prepared                                  From Chromium-Iron Promoted Thiomolybdate                                     Precursor F Prepared With Diethylenetriamine*                                 Catalyst Hours                                                                on Stream       % HDS    % HDN                                                ______________________________________                                        42              55.9     83.5                                                 46              56.2     83.5                                                 ______________________________________                                         *LSHV 4.0                                                                

A 13 cc sample of catalyst derived from Precursor G (Example 7) was usedto hydrotreat the LCCO feed at a LHSV of 3.0 over a period of 120 hrs.The second order hydrodesulfurization (K_(HDS)) and the first orderhydrodenitrogenation (K_(HDN)) rate constants for this catalyst werecalculated to be K_(HDS) =2.7 and K_(HDN) =4.0. The HDN selectivity(K_(HDN) /K_(HDS)) was therefore 1.5.

At the same conditions, the K_(HDS), K_(HDN) and K_(HDN) /K_(HDS)obtained using the commercial nickel molybdate on alumina catalyst were12.2, 1.29 and 0.1, respectively.

The hydrodenitrogenation activity, per unit of active (Mo) metalcontent, of the excess chromia supported Fe-Cr-Mo sulfide catalystderived from Precursor G was the highest of any supported catalystspecies tested. It was also better than that of comparable Cr-Mosulfide, Ni-Mo sulfide, Ni-W sulfide, Mn-Mo sulfide catalysts supportedon chromia, and far superior to that of the above species supported onother inorganic refractory oxide carriers like silica, alumina or ironoxide.

A sample of catalyst derived from Precursor H (Example 8) was run onLCCO. This gave a second order hydrodesulfurization rate constant of1.37 and a first order hydrodesulfurization rate constant of 0.14.

EXAMPLE 13 Comparative Example

In this experiment, a chromium-promoted molybdenum sulfide on aluminacatalyst was prepared using the procedure set forth in Example 4 of U.S.Pat. No. 3,265,615. Thus, 24.2 grams of (NH₄)₆ MoO₇ O₂₄.4H₂ O (APM) weredissolved in 150 ml of water. One-half of this solution was used toimpregnate 26.6 grams of a reforming grade γ-Al₂ O₃ that had beencalcined to remove water. The impregnate was dried overnight at 100° C.and reimpregnated with the other half of the APM solution. The resultingimpregnate was again dried overnight at 100° C. and then calcined in airfor four hours at 550° C. To the calcined impregnate was added a hot(80°-100° C.) solution of 20 g of Cr₂ (SO₄)₃ in 50 ml of water, followedby drying overnight at 100° C. to form 58.7 g of a green colored,chromium-promoted molybdate precursor. This precursor was thenpelletized and screened to 20 to +40 mesh.

The screened precursor was placed in the reactor and contacted withflowing hydrogen at room temperature. The temperature was then raised to288° C. and held there for one-half hour, followed by raising thetemperature to 450° C., holding for one-half hour and then raised to510° C. and held at 510° C. for one-half hour. The reactor temperaturewas then lowered to 316° C., and the hydrogen replaced with a 10% H₂ Sin H₂ mixture. The flowing H₂ S/H₂ mixture contacted the precursor forthree hours at 316° C. The LCCO feed was then introduced employing theprocedure set forth above, except that the LHSV was 3.0 V/V/hr. Theresults are set forth below in Table 7.

                  TABLE 7                                                         ______________________________________                                        Catalyst Hours                                                                on Stream       % HDS    % HDN                                                ______________________________________                                        48              23.8     5.8                                                  70              24.4     5.2                                                  ______________________________________                                    

These results are much different from the results obtained for achromium-promoted molybdenum sulfide catalyst of this inventionemploying the same feed and reaction conditions set forth in Table 3.Thus, the chromium promoted catalyst of this invention is much superiorin both HDS and HDN activity to the chromium promoted catalyst disclosedand claimed in U.S. Pat. No. 3,265,615. These comparative results alsoestablished that the catalyst of this invention is a different catalystfrom that of U.S. Pat. No. 3,265,615.

EXAMPLE 14 Preparation of Precursor I and Catalyst Therefrom

174.8 g of a 22 wt.% aqueous suspension of colloidal Cr₂ O₃ containing38.46 g of Cr₂ O₃ (0.25 m Cr₂ O₃), was placed into a 2000 mlround-bottom flask provided with an electric stirrer, and diluted to 400ml with distilled water. 15.66 g of (NH₄)₂ MoS₄ (0.06 m) was dissolvedin a mixture of 100 ml H₂ O and 50 ml ethylenediamine (en) in an icebath, and the resulting solution was slowly added to the colloidal Cr₂O₃ suspension with rapid agitation. Some gel formed, which was broken upwith a spatula, and a small quantity of additional water was added tothe system. After the thiomolybdate addition was completed, 16.18 g ofCr(en)₃ Cl₃.3.5H₂ O (0.04 m) dissolved in 50 ml water was added to theround-bottom flask. The slurry turned bright orange. Stirring wascontinued for 15 more minutes, after which the mixture was filtered andwashed with water. The solid was dried in a vacuum at 50° C., and asample of the filter cake was ground and sieved to 20/40 mesh. Analysisof the catalyst precursor (Precursor I) showed 25.0 wt.% Cr, 4.94 wt.%Mo, or a Mo/Cr atomic ratio of 1/9.3.

Sulfiding of the precursor was done for three hours at 325° C. with aten percent H₂ S in H₂ mixture.

Evaluation of the resultant composition as a catalyst was carried out inan automated, continuous stirred tank reactor unit consisting of a oneliter autoclave, calibrated feed burette, pump, gas-liquid separator,and product liquid collector. In a typical experiment, 20 cc of catalystwere charged in a stainless steel basket which was placed inside theautoclave.

Operating conditions and hydrotreating results are listed in Table 8.

                  TABLE 8                                                         ______________________________________                                        Operating Conditions and Hydrotreating Results                                ______________________________________                                        Feed                   LCCO                                                   Properties             See Table 1                                            Temperature, °C.                                                                              325                                                    Pressure, MPa          3.15                                                   Hydrogen Rate, SCF/bbl 3000                                                   Space Velocity,, V/V/hr                                                                              1                                                      % HDS                  26.8                                                   % HDN                  29.9                                                   ______________________________________                                    

What is claimed is:
 1. A hydrocracking process comprising contacting ahydrocarbon feed at a temperature of at least about 100° C. and in thepresence of hydrogen, with a catalyst obtained by compositing a quantityof inorganic refractory oxide support material with one or moreprecursor salts and heating said composite at elevated temperature of atleast about 150° C., in the presence of sulfur or sulfur bearingcompound and under oxygen-free conditions for a time sufficient to formsaid catalyst, wherein said precursor salt contains a tetrathiometallateanion of Mo, W or mixture thereof and a cation comprising trivalentchromium or a mixture of trivalent chromium with one or more divalentpromoter metals selected from the group consisting of Fe, Ni, Co, Mn,Zn, and Cu wherein said trivalent chromium and divalent promoter metalsare chelated by at least one neutral, nitrogen-containing polydentateligand, L, and wherein said feed contacts said catalyst for a timesufficient to hydrocrack at least a portion of said feed.
 2. The processof claim 1 wherein said tetrathiometallate salt is selected from thegroup consisting of [Cr_(1-z) M_(z) LX_(y) ][MoS₄ ]_(n), [Cr_(1-z) M_(z)LX_(y) ][WS₄ ]_(n) and mixture thereof wherein the chromium is in thetrivalent state, wherein n=(3-z-y)/2, wherein M is one or more divalentpromoter metals selected from the group consisting of Mn, Fe, Co, Ni,Cu, and Zn, wherein 1>z≧0 and 1-z≧y≧0, wherein L is one or more neutralnitrogen-containing ligands, at least one of which is a chelatingpolydentate ligand, and wherein X is a singly charged anionic ligand. 3.The process of claim 2 wherein said precursor salt is formed in thepresence of a slurry of particles of support material.
 4. The process ofany claims 1, 2, or 3 wherein ligand L is selected from the groupconsisting of alkyl amines, aryl amines, nitrogen heterocycles andmixtures thereof.
 5. The process of claim 4 wherein ligand L comprisesan alkyl amine.
 6. The process of claim 1 wherein said catalyst containsat least one of said promoter metals.
 7. The process of claim 4 whereinsaid catalyst contains at least one of said promoter metals.
 8. Theprocess of claim 7 wherein said catalyst is formed in the presence ofexcess sulfur.
 9. A process for hydrotreating a hydrocarbon feed whichcomprises contacting said feed at a temperature of at least about 150°C. and in the presence of hydrogen with a catalyst obtained bycompositing a quantity of inorganic refractory oxide support materialwith one or more precursor salts and heating said composite at elevatedtemperature of at least about 150° C., in the presence of excess sulfurin the form of one or more sulfur-bearing compounds and underoxygen-free conditions for a time sufficient to form said catalyst,wherein said precursor salt contains a tetrathiometallate anion of Mo, Wor mixture thereof and a cation comprising trivalent chromium or amixture of trivalent chromium with one or more divalent promoter metalsselected from the group consisting of Fe, Ni, Co, Mn, Zn, and Cu whereinsaid trivalent chromium and divalent promoter metals are chelated by atleast one neutral, nitrogen-containing polydentate ligand, L, saidcontacting occurring for a time sufficient to hydrotreat at least aportion of said feed.
 10. The process of claim 9 wherein saidtetrarthiometaleate salt is selected fron the group consisting of[Cr_(1-z) M_(z) LX_(y) ][MoS₄ ]_(n), [Cr_(1-z) M_(z) LX_(y) ][WS₄ ]_(n)and mixture thereof wherein the chromium is in the trivalent state,wherein n=(3-z-y(/2, wherein M is one or more divalent promoter metalsselected from the group consisting of Mn, Fe, Co, Ni, Cu, and Zn,wherein 1>0 and 1-z>y>0, wherein L is one or more neutralnitrogen-containing ligands, at least one of which is a chelatingpolydentate ligand, and wherein X is a singly charged anionic ligand.11. The process of claim 9 wherein said precursor salt is formed in thepresence of a slurry of particles of support material.
 12. The processof claim 11 wherein said tetrathiometallate salt is selected from thegroup consisting of [Cr_(1-z) M_(z) LX_(y) ][MoS₄ ]_(n), [Cr_(1-z) M_(z)LX_(y) ][WS₄ ]_(n) and mixture thereof wherein the chromium is in thetrivalent state, wherein n=(3-z-y)/2, wherein M is one or more divalentpromoter metals selected from the group consisting of Mn, Fe, Co, Ni,Cu, and Zn, wherein 1>z≧0 and 1-z≧y0, wherein L is one or more neutralnitrogen-containing ligands, at least one of which is a chelatingpolydentate ligand, and wherein X is a singly charged anionic ligand.13. The process of any of claims 9, 11, or 12 wherein ligand L isselected from the group consisting of alkyl amines, aryl amines,nitrogen heterocycles and mixtures thereof.
 14. The process of claim 13wherein ligand L comprises an alkyl amine.
 15. The process of claim 9wherein said catalyst contains at least one of said promoter metals. 16.The process of claim 13 wherein said catalyst contains at least one ofsaid promoter metals.
 17. The process of claim 9 wherein said feed is alube oil fraction.
 18. The process of claim 13 wherein said feed is alube oil fraction.
 19. The process of claim 16 wherein said feed is alube oil fraction.
 20. A process for removing nitrogen from anitrogen-containing hydrocarbon feed which comprises contacting saidfeed at a temperature of at least about 150° C. and in the presence ofhydrogen with a catalyst obtained by compositing a quantity of inorganicrefractory oxide support material with one or more precursor salts andheating said composite at elevated temperature of at least about 150°C., in the presence of excess sulfur in the form of one or moresulfur-bearing compounds and under oxygen-free conditions for a timesufficient to form said catalyst, wherein said precursor salt contains atetrathiometallate anion of Mo, W or mixture thereof and a cationcomprising trivalent chromium or a mixture of trivalent chromium withone or more divalent promoter metals selected from the group consistingof Fe, Ni, Co, Mn, Zn, and Cu wherein said trivalent chromium anddivalent promoter metals are chelated by at least one neutral,nitrogen-containing polydentate ligand, L, said contacting occurring fora time sufficient to remove at least a portion of nitrogen from saidfeed.
 21. The process of claim 20 wherein said tetrathiometallate saltis selected from the group consisting of [Cr_(1-z) M_(z) LX_(y) ][MoS₄]_(n), [Cr_(1-z) M_(z) LX_(y) ][WS₄ ]_(n) and mixture thereof whereinthe chromium is in the trivalent state, wherein n=(3-z-y)/2, wherein Mis one or more divalent promoter metals selected from the groupconsisting of Mn, Fe, Co, Ni, Cu, and Zn, wherein 1>z≧0 and 1-z≧y≧0,wherein L is one or more neutral nitrogen-containing ligands, at leastone of which is a chelating polydentate ligand, and wherein X is asingly charged anionic ligand.
 22. The process of claim 21 wherein saidsalt is formed in the presence of a slurry or support material.
 23. Theprocess of any of claims 20, 21, or 22 wherein ligand L is selected fromthe group consisting of alkyl amines, aryl amines, nitrogen heterocyclesand mixtures thereof.
 24. The process of claim 23 wherein ligand Lcomprises an alkyl amine.
 25. The process of claim 24 wherein saidcatalyst contains at least one of said promoter metals.
 26. The processof claim 25 wherein said feed is a lube oil fraction.
 27. A process forimproving the oxidation stability of a nitrogen and sulfur containinglube oil feed which comprises contacting said feed at a temperature ofat least about 150° C. and in the presence of hydrogen with a catalystobtained by compositing a quantity of inorganic refractory oxide supportmaterial with one or more precursor salts and heating said composite atelevated temperature of at least about 150° C., in the presence ofexcess sulfur in the form of one or more sulfur-bearing compounds andunder oxygen-free conditions for a time sufficient to form saidcatalyst, wherein said precursor salt contains tetrathiometallate anionof Mo, W or mixture thereof and a cation comprising trivalent chromiumor a mixture of trivalent chromium with one or more divalent promotermetals selected from the group consisting of Fe, Ni, Co, Mn, Zn, and Cuwherein said trivalent chromium and divalent promoter metals arechelated by at least one neutral, nitrogen-containing polydentateligand, said contacting occurring for a time sufficient to improve theoxidation stability of said feed.